Beef and Tortilla Bake

1 pound ground beef
1 C chopped onion
1 (10oz) can enchilada sauce
1 (8oz) can tomato sauce
1 (16oz) can refried beans
2/3 C evaporated milk
5oz tortilla chips, slightly crushed, plus 2oz whole chips
1 C shredded Monterey Jack cheese

Preheat oven to 375. Heat a medium skillet over medium-high heat; add beef and onion. Cook until beef is browned and crumbly, about 10 minutes; drain well. Add enchilada sauce and tomato sauce to skillet; stir well. Cook until slightly thickened, about 10 minutes. Spoon beef mixture into a 2-quart baking dish. Combine beans and evaporated milk in small bowl. Spread over beef mixture. Arrange whole tortilla chips around edge of dish. Top casserole with crushed chips; sprinkle with cheese. Bake until hot and bubbly, about 20 minutes.